The present invention relates to testing units by which an operator can select and test communication links of a communication system that links an intermediate station to remote stations, and to a method of testing these links.
Known in the art, there is the U.S. Pat. No. 4,998,240 granted on Mar. 5, 1991, and naming Clifton B. WILLIAMS as the inventor. This patent describes a system and a method for remote and unattended testing of a ISDN protocol at a central office. An object of this invention is to test customer ISDN lines without the necessity to dispatch personnel to a customer site or central office.
In the system described in U.S. Pat. No. 4,998,240, the link connecting the equipments to be verified is also used for sending command signals relating to the test to be performed. Accordingly, if the link is broken or cannot efficiently convey the data signal, then it is not possible to do a test. Also, the nature of the tests that are performed is very specific and relates to the verification of transmission protocol and data integrity. These tests do not provide any information on the quality of the link itself. Also, the system can only operate with AT&T (trademark) equipment and uses functions already programmed in the system.
Also known in the art, there is the U.S. Pat. No. 4,055,808 granted on Oct. 25, 1977, naming Jerry L. HOLSINGER et al. as inventors. In this patent, there is described an intermediate location testing unit for connection to a communication unit located at an intermediate location in a data communication network. The network additionally includes first data transmission means for conveying signals to an upstream port of the communication network from a central location. The communication unit also includes a downstream port for conveying signals to other data transmission means that connect to remote locations. The signals have first characteristics at the upstream port and second characteristics at the downstream port. The data communication network further includes a central testing unit at the central location for transmitting a test control word having a command portion and an address portion. The system uses an address command protocol within a test control word circulating within the communication data network. With this system, it is not possible to verify circuits that are out of order to the point where they cannot receive or transmit the test control word. There is also no direct communication between the central station and the remote stations.
Also known in the art, there are the following U.S. patents describing different testing apparatus and methods for testing a communication system:
U.S. Pat. No. 5,027,343 (CHAN et al.) PA1 U.S. Pat. No. 4,945,554 (KRAUSE et al.) PA1 U.S. Pat. No. 4,937,851 (LYNCH et al.) PA1 U.S. Pat. No. 4,918,623 (LOCKITT et al.) PA1 U.S. Pat. No. 4,682,347 (LYNCH) PA1 U.S. Pat. No. 4,611,101 (WALTER et al.) PA1 U.S. Pat. No. 4,419,751 (CHOLAT-NAMY et al.) PA1 U.S. Pat. No. 4,076,961 (HOLSINGER et al.) PA1 a first communication link for receiving and transmitting signals generated from a computer, said first communication link being part of said second communication system; PA1 a control unit connected to said first communication link for receiving and transmitting signals therefrom; PA1 a second communication link connected to said control unit for receiving and transmitting signals therefrom, said second communication link being part of said second communication system so that communication can be established between said computer and said remote stations via said intermediate station by means of said second communication system; PA1 a signal generating and measuring device connected to said control unit, having an input for receiving a signal to be measured and an output for generating a predetermined signal; PA1 a switching system controlled by said control unit and interconnecting the corresponding communication links of the first system with said generating and measuring device, by which one of the corresponding communication links can be selected by said control unit and connected to said input and output of said signal generating and measuring device; whereby said operator can select at least one of said links between said intermediate station and one of said remote stations by sending command signals via said second communication system, and monitor a test procedure on said link that has been selected by said operator via said second communication system. PA1 (a) establishing a first connection between said computer and said intermediate station, upon commands issued from said computer; PA1 (b) establishing a second connection between said intermediate station and one of said remote stations that has been selected by said operator, upon commands issued from said computer for selecting a communication link between said intermediate station and the remote station that has been selected; PA1 (c) sending command signals to said testing unit via said first connection for initiating a test procedure on said communication link that has been selected, upon commands issued from said computer; and PA1 (d) transmission of results of said test procedure from said testing unit to said computer via said first connection, whereby an operator can select a particular communication link by means of step (b), initiate said test procedure on said particular link by means of step (c) and be informed of the result of said test procedure by means of step (d).
One drawback with all of these testing apparatus and methods resides in the fact that if a communication link of the system is totally out of order or deficient to the point where it cannot transmit information, it is not possible to perform a test on this link.
Accordingly, an object of the present invention is to provide a testing unit and a testing method by which an operator can select and test communication links of a communication system even if this communication link is out of order or broken down.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non restrictive description of a preferred embodiment thereof, given for the purpose of exemplification only with reference to the accompanying drawings.